Process of extracting iron from clay



Patented July 24, 1951 inf a PROCESS OF EXTRACTING IRON FROM r CLAY 1 Hubert A. Shabaker, Media, Pa., Iassignor to" "Houdry'ProcessCorporation,

' a corporation of Delaware 125 I ,4 amming :The" .present invention relates to" improved Application September Serial No. 774,439 e 13 Claims. (01. 252-450 methods of treating clay for the. preparation therefrom of aotive'fcontact masses particularly useful as proc s 1 In cop ndi g 'appiicatmhs' Serial A has. 644,423

andj fiSlgiZG (filed jointly in the names of myself, George Alexander Mills and Ruth C. Denison) catalysts' jin hydrocarbon conversion wi lmingt on', Del.,

In effect n reaction betweeh the mm present "inclays with a sulfiding gas only a small quantity of e the, gas is theoretically required. For instance,

ifjjhydrogen sulfide is utilized as the sulfiding agent, thereaction may be postulated in accordancel'with either of thefollowing equations:

are described for the production of contact masses providing catalysts ofunique properties, by treatment of clays with sulfiding gases at elevated tem perature followed by the removal of the iron or it carbon disulfide is employed, the reaction may belpostulated in accordance with the follow-,-

sulfide thus formed. The novel contact'masses thus obtained are changed in physical and chemicfalffproperties and demonstrate important advantagesas-catalysts including exceptional stability in cracking or treating petroleum stocks of high sulfur content." By the present invention further improvements in these described methods of;clay treatment are provided, affording importantadvantages in the practical operation thereof from the standpoint of efficiency and economy of operation, resulting more consistently and uniformly in"iiltimateproducts of desired quality.

These advantages are obtained, in accordance with one aspect of the present inveiati'on', by the use of a hot gaseous carrier medium for the dilution of the active sulfiding gas, andby utilizing the sensible heateontent of the gaseous carrier for heating up the clay to and maintaining-the same as desired treating temperature. The gaseous heat carrier, moreover, serves as a heat transfer'medium levelling out any changes in tem-' perature that might tend to occur as a result of exothermic or endothermic reactions taking place, thereby providing better controlto maintain uniformity in desired temperature conditions during treatment of the clay. Only a small amount of sulfiding gas is theoretically required for reaction with the iron content of the clay being treated, but it is preferedi to employseveral times that amount, as will hereinafter appear. By using the thus diluted sulfiding gas, it has been found, not only is waste of comparatively, more expensive active sulfiding gas avoided and extensive corr'o'sion of the treating apparatus by sulfides at these high temperatures greatly diminished, but the operation further provides a thorough and rapid flushing of undesirable reaction and/or calcination products from the treatedclay. Inaddition, the removal, as by acid leachingof the iron sulfides formed, is surprisinglyfacilitated. Accordingly, better, control of the sulfidation' reaction is afforded, and more uniform production of products or superior quality assured/ g 3 I g in thefabove equations, it isassumed, that the Q ironcontent' of the, clay; is present largely inferric conditioxrwhichwillserve adequately as a basis for discussion. The weight ratio of I-IzS/FezOa is;

the :isame; in both, Equations I and II, being 0.64/10,- therefore :thetheoretical amount of HaS required may be takenas 0.64 pound of Hasperh pound of: FezOa in the clay. This quantity of H23 is far from sufficient to heat the clay to the,

-It-has been found thatabout 1000 to 1300 vol-'- umes of, gas Kbased un air) are required to heat one volume of clay from room temperature to 1400?. F consideringtapelleted clay, such as an,

acid-activated montmorillonite clay, weighing about 45, pounds per cubic foot. With such clay containing 2.0%; 1FezOa, the theoretical requirement of H28 would be 0.576 pound, or only about 6.5 cubic ieetof, H28 per cubic foot of clay. In thecaseof CS: (Equations III and IV above) the weight ratio of CSz/FezOa in either equation is ,,0 .f7l5/1. 0, which cangbe taken as the minimum theoretical amount ,ofpCSz required to sulfide all the iron .inthe clay which again would be insufw ficientto provide the amount of gas required for heating the clay. 1

accordance the c1ay ..to; desired temperature for the sulfiding reaction so that other; means of preheating the clay are unnecessary,,while only a small amount of theac ive sulfiding; gas'is used to efitect the In th' [selection of the 1 H r ith, the invention, the gaseous carrier medium provides the heat for bringing,

gaseous carrier as the heating, medium, consideration must be given to its composition andproperties. The carrier gasv must' 'befessentially inert; ,that is. it must be tree T from oxidizing constituents which would consume the active sulfiding gas, and also free from other constituents in amounts which would interfere with the sulfidation reaction .or. be harm-. ful to theficatalyst; Commercial nitrogen; isan example of a gas fulfilling these requirements, and has been successfully employed in accordance then;.Tcor'ita in components such as. water vapor,.

C02,. and generally? small amounts of CO and Hz in. addition to nitrogen. It was 'foundfitliat the presence of substantialamounts of water vapor or large amounts .of CO2. inlthetreating gas at the elevated temperature of treatment of the clay was deleterious, inithat the .sulfiding action was impeded and'.catalystsnof lower-activity were obtained.

Flue gas, however, can be processed'to modify or substantially reduce or're'mo've theinterfering. and deleterious constituents. For instance, water vapor canabe removedby-drying the gas over desiccants or selective. .absorbents. Substantially complete removal of 002 could be obtained by caustic washing. A 1 more attractive: and: less expensive-processReflecting: removal of C021 to below deleterious concentrations; as. down toabout..1!; av CO2, isavailable in the Girbirtol amineprocess'.

In accordance with-this process the flue" gas :is passed in countercurrentrelationship. to a suitable amine, such as ethanolamine, atconditionsof temperature and. rate of flow such that the acid gas is completely stripped: from the other gases by reaction with the amine solution, by the:

formationof acompound which is'subsequently dissociated'by" the application of heat. For-ex amplatlieamine solutionmenters an absorber near the top 1 and flows in 'countercurrent: rela-' tion to the=rising gas, absorbing carbon dioxide in its' downward passage; with purified gas emerg ing' from-the top of the absorber.- The rich aminesolution containing the removed 'acid gasis trans-- ferr'ed'to a reactivator, which may be similar" apacke'd tower, in which the rich solution isdirectly or indirectly heated as it flows through the tower andthe dissociatedacid gas is strippedfrom thehot amine solution as with steam. "De-- tails of this process are-described in-U. S. Patent Re. 18,958. Y

Experiments conducted using'gaseous carriers having the composition df"-a dried, Girbii'to'l treated flue gas, demonstrated this composition to-be successful as a heating carrier gas for'sulfiding gas such as Hes. Another aspect of 'tl'ie present invention,ftherefore, involves the use" as a c'arrier for sulfidin'g gas of a specially processed flue gas substantially free from" oxidizingcon' stituents' and water' vapor and containing not more than about by volume of CO2 Although the'described Girbi'rtol" precession theremoval of CO2 from .flue gas;is.;less cost ly than -;otner; methodsfisuch. as caustic. wash, the use of such procedure sti'll'introduces an item ofexpense which might desirably heeliininetted.

Ihav further "discovered that" the step" 'of remov- Such flue ing CO2 from the flue gas need not be'practlced and the process of the invention considerably simplified by overcoming the inhibiting effect of he 2. n t e.su fi pperatiea. .Th sc be accomplished, in. ,;=accordanc 5a: preferred. aspect of'the present invention, y the use of somewhat larger amounts of sulfiding gas, as in excess of twice the stoichiometric equivalent require'd tcr react with the iron content of the clay.

To readily obtain the desired low residual iron ,cOntentonsubsequent. acid leaching with diluted .jsulfiding"..gascontaining in the order of about ll) to 1' 5 %,CO2, there should be employed an amount of active sulfiding gas of at least about 3 to 4 times"'thedstoichiometric equivalent of the iron content of the clay. Acceptable results are generallyrobtained if the volume ratio COz/HzS does not exceed about 10. Higher concentrations of sulfiding. gas may be employed, but .noparticular advantages are obtained musing .quantitiesQof sulfiding gas in excess ofabdut.1'O%- by volume.

concentration the inert heat" carrier gas, while amounts over 25% mey'seerificeeertain of..t e.

advantagesof the present invention, suchas low cost of. gas, inhibition of. the corrosive eif'ec't, and particularlytheifacilityof subsequent ac'id' leaching assuring. umrerm; production; 0? catalysts or: .su erior.qua1ities.'

"It will" be .seen from. the. foregoing, that the composition or the treating gas including; the.. concentration of active.sulfidingflagent asI-well'.

as the. kind and quantity} of constituents 'inthe.

. gaseous carrier. medium are. importantfin obtaine ing, modified. clays providing catalysts of sign activity andother .desired, physicaland chemicalproperties. .Oxygen' and water. vapor: should best be. eliminated; or. reduced-to insignificant .quantities. to; the- .order of. less. than 0 l volume. percenti, although water vapor up.-to.ab out; 2 to. 3%.

bylvolumeof total treating, gas. may be tolerated. Nitrogen in. substantially. pure. form, as has al.-. ready been indicated. onin. admixture. with oer- ..tain.-.oth'er gaseous constituents non-reactive.

with clay.componentsprovidesa .s-uitable inert heat carrier medium. .Carbon dioxide, on the.

other hand is undesirable in the carrier gas. inlarge amounts. -Whenused 'alone-, or as acon sti'tuent of. a-carrierigas containing.1=0.%-or more CO2; and only small amounts .ofi sulfiding gas less than-twice thetheoretical amount required to react with. the. iron. content. otthe; clay,,.therewas. not obtained.v on. subsequent, acid; leachingeof.

the clays investigated. catalysts ofkthe desired tratiens efH'zs. intheftreating'fgas, but was less.

'iew iron.con.tent. :Smallamountsaof CO in the.

nitrogenouscarrier. gas. ..'('as below about. 5 by volume) were not. found. tov have any definiteinterf'eringl efi'ect. and there were. indications that the presence effCO may-even. befbeneficial, particularly when there was present an amount of. active sulfid'ing gas in, excess of twice the theo-,.

reti'cal. iron equivalent... 1 Hydrogen washfoundnt have "aretarding' action .on very dilute concen-- "-proneuncedie 'thefI-ES concentration was .i'n

creased! With. no significant. retarding-, 'effectl observedwhenthe quantity of. was raised to the order of about 2 or. more 'mol; percent, provvid'ed the quantity df'Hz-waslnot too great as will"- "hereinafter appear} Small amounts of. CO2 pres.

ent f in the. nitrogenous, gas, however, as in the. order of'l toi21volumepercent, .di'd nothaveany noticeable. adverse effect. $Mo'reover, it was. found. .that' the inhibiting; aetioniof'coz present inthe gas'in'the. order ofabove about101%v by ve1ume,:

" could be ess'entiallycorrected bythe use of larger amen-42a quantities of active sulfiding gas-as hasalready been pointed out. Here too, the presence of small amounts of CO as in the range of 0.5 to 5 volume percent may be beneficial in tending to overcome the inhibitory effect of the CO2 on the sulfidation reaction. Thus, a fiue gas containing about llto 13 volume percent CO2 canbe successfully employed if the proper quantity of active sulfiding gas is used. Addition of CO to themixture tends to diminish the retarding action of the CO2 but in the presence of H2 very little effect is apparently exerted by the C0. The

amount of H2 in the mixture is of major importance. Oneor two percent of H2 added to a gaseous composition comprising N2, CO2, and CO does not appear to exert much retarding action, but larger. amounts of H2 exert rapidly increasing retarding effect, decreasing with higher H25 contents. In all cases the retarding efiects of the CO2, CO, and H2 mixtures are decreased as the amount of H255 is increased. Thus, all retarding effects are in the direction of lower Has to CO2, CO, and H2 ratios.

In the. carefully controlled combustion of a gas such as propane for the production of a suitable fi ue gas, a gas-air mixture which would insure less than 0.1% Oz in the flue gas would also produce about 0.5% CO and some H2 in the flue gas. The CO and H2 content of the flue gas can be increased within limits by proper control of the air-propane mixture. To get essentially oxygen in the flue gas from the burning of propane, the flame must be held slightly on the reducing side which results in the formation of about 0.5% CO. At this concentration of C0 that of CO2 about 12%, all on avolume basis.

The proportions of CO2, H2, CO and H20 in a flue gas are determined by the theoretical equation CO2+H2=CO+H2O which in accordance with the law of mass action would be governed by an equilibrium constant at any particular temperature. It has been calculated that in the equilibrium formula sage through the bed of clay, so that the deacti vation effect of the less than equilibrium amount ofwater which was formed was comparatively '35 the probable H2 content will be about 2.5% and fiding gas, uniformly successful leaching :was

readily obtained at room temperature.

' It is indicated in the prior applications the. 1

catalysts of advantageously improved properties are obtained by sulfiding with His at about 1200 F. and up to short of the temperatures causing incipient fusionor rapid shrinkage of the clay; somewhat higher temperatures are indicated for CS2, as above about 1300 F. These conditions apply in the use of diluted sulfiding gas, with optimum results being obtained with most clays investigated generally in the range of about 1350-1450 F.; 1400 F. being found a convenient and safe operating temperature. The temperature limits for any particular clay are fixed by catalyst activity on the one hand and residual iron content on the other; too low a temperature resulting in inefiicient sulfidation and by too high a temperature of sulfidation catalysts of reduced activity are obtained.

In the indicated temperature range, the rate of for the sulfidation reaction. flue gas containing an amount of sulfiding gas of about Stimes the theoretical equivalent of iron in the clay to overcome the inhibiting effect of.

CO2 and other constituents (84.1% N2, 11.5% CO2 2.5% H2, 0.5% CO and 1.4% Hes, all by volume), the iron content of an acid activated montmoril-. lonite clay (originally 2.1% F8203) was reduced to below 0.2% F8203 by a 5 hour treatment (followed by acid leaching), whereas in a 2 hour treatment using a treating gas of the same composition the residual iron content of the clay after acid leaching was about.0.32%. With somewhat higher concentrations of active sulfiding to remove sulfates.

insignificant or within the limits of experimental 1 error in measurement and testing of catalyst activity. It has already been indicated above, that by the use of the diluted sulfiding gas, the formed iron sulfide was more easily removed by subsequent acid 1eaching,whereas in the case of Has or other high concentrations of sulfiding gas, catalysts of less than 0.2 to 0.1% F6203 are percent and at temperature in excess of about 1300 to 1350 F., however, the difference is, largely wiped out. As a general rule, the same volume concentrations of CS2 may be employed as has already been indicated in connection with Has as the sulfiding agent.

EXAIVIPLE I The clay treated in this example was a commercial acid-activated montmorillonite clay (Filtrol), having the following analysis on a dry C.) basis; in some of these experiments the clay employed was previously washed with water This step did not appear to have any material effect on the ultimate results obtained by the invention. 1

Parts by weight Unwashed Washed Loss 1600 F.) 8. 51 7. 84

Sias sioi 64.4 67.8

A1 as A1203..- 15.64 16.5

r (a) The clay was ground, admixed with water to suitable consistency and extruded as pellets of;

' 4 .2mm; diameter and-4 gamma mm.:lengths. The'pellets were dried and then variously treated a's shown below. The iron content of the final catalystin each; instance was determined as well as its acdut in the crackingof hydrocarbons (after calcination .in air at 1050 F. for 2 hours); the; resultsbeing shown in Table lbelow.

' (1))A' portion of the pellets were treated at 1.400 F. for 5 and 8 hours'respectivelywith a gas mixture comprising 99.18% nitrogen and 0.82%- H'zS (by vol.)', subsequently permitted-to cooland treated with 15% aqueous 'HCl solution for 24 hours at room temperature; followed bywashing; in water and drying. 1

' Another portion of the pellets from (a) above was treated "at 1400 Fafor hours with hydrogen sulfide: in various concentrations car tied: in a nitrogenous: gas comprising: or simulatv ing'aprocess'ed flue gas free from water but of different content of 002, Hz, and CO. The sulfided pellets were thenacid leached asin the-precedingiparagraph. The efi'ects of varyingthe concentration of the sulfiding gas and the com--. position'xof' the carrier gas is shownin Ilable 1 below. V

(d) For comparison, other treatments of the pelleted catalyst were conducted'at 14=0Oj F. 'ior 5; hourswithi'hy'drogen sulfide carried indry carbo'n' dioxide gas and (c) with nitrogenous gas containing watemi'likewise' followed by'acid'leach- 30 ing. These results: are also tabulated-in Table 1'.

deposited on the catalyst is determined by conversion to CO2 and expressedin weight per-cent o1 charge. gaseous by products is: also determined and the weight percent of gas c'alculated from the meas ured -volume and" gravity. a

I A number of the: experiments shown in Table 1 were repeated withvariationsinduratiorrot treatment (at 1 2 /2, and 10 hours) and in tem-'' perature of treatment (at intervals fromu1300: to 1475 E). These'experiments showed that for the particular clay and the treating conditions.

effect as the concentration of sulfiding. 'gas'.

is increased. To assurethe consistent production? of catalysts having less than 0.2% residual F8205 larger quantities and higher concentrationsof j H28 should be employed as above 2.5 mol percent 1128 in themixture, or providingmore than} times the equivalent of iron present.

A number of the experiments were repeated with other'acid activated montmorillonite clays and with other available clays having 2 to' over 5% F6203.

confirmed the previous experiments. Although .for any particular 7 clay somewhat larger or" smaller quantities of sulfiding. gas may be re- Table! Treating Gas Oomp., Vol. percent Finished Catalyst Oat-Al Activity liesidiiilal 1 ton Leached Wt. ratio EDS/Fem; 1 Gas0., Coke, Gas, Gm pai -Q83 N G0 H O Hz CO HgS Hrs V01. Wt. Wt. Per i Per Cent Per Cent Per Cent While the above treated catalysts under (1)) and (0) above showed gasoline yields in cracking of a light gas oilunder standard conditions of 37-39%, by volume of the charge, when the nitro- 'genous' gas was substituted by C02 ((1) or when as much as 5% *H2OWas present in the treating gas (e) not only wasxiron removal impeded, but the resulting catalysts showed reduction in gasoline'activity and"comparatively high coke at the particular level of activity. I ,y

r The gasoline yields shown in the above table and elsewhere herein referred'to are those obtained by theCAT-A method, described by H. G.

Shimp and J. A. Alexander in National Petroleum above clay in the same manner as described in quired in practice for best'results, the indicated quantities should be found generally" applicable.

EXAMPLE II The clay treated in this example was froma.

diirerent lot of commercial acid-activated 1110111}! morillonite clay having thefollowing analysls on av dry C.) basis:

Ing. loss 1600" F.) a 9.2 Si as S102 64.4..

A1 as A1203 v ..14.3 Fe as F8203 1.57 Na as N320! 0.11 K as K20 -4- 20.20 Ca as CaO 2.66. Mg as-MgO Mud--- 556 S04 4.1-8

(a) Pellets were prepared by extrusion of the Example I, paragraph (a). I

(b) The above pellets were treated for 5 hours at-;1400 F. with various carbon disulfide com; positions in an essentially inert carrier. gasfol- The gravity (referred to air) of the;

Although there were individual 'quantitive variations, in allinstances the results lowed by acidrleachingawiththe. results shown in ili fq lew e ia la i For comparison, pellets of the same clay were in nitrogen in an amount giving a weight ratio of Has/F6203 of 10.3 (75% N2-25% HzS), followed by acid leaching; the resulting catalyst contained 0.1% F9203.

In employing flue gas as the heat carrier medium, the composition of the gas may be controlled by the amount of air supplied in burning the fuel. The limits will be more or less fixed in order to obtain a minimum of free oxygen in the flue gas on the one hand, and for limiting the quantity of uncombined hydrogen on the other. In using commercial propane as a fuel, for instance, suitable flue gas for use in accordance with the invention may be obtained by controlling combustion so as to obtain in the flue gas about 0.5 to 3% hydrogen. Under these conditions there will be formed approximately 1.0 to 4.5% CO, 11 to 13% CO2, the balance of 85 to 81.5% being chiefly nitrogen, which may contain very small amounts of other inert gases.

Thus, a flue gas was prepared, by burning propane and drying, containing (by volume) 1.3% Hz, 1.6% CO, 12.7% 002, 0.02% 02, the remain ing about 84.4% being essentially N2. To this gas was added 2.1 volume percent I-IzS and employed for sulfldation of clays as illustrated in the following example:

EXAMPLE III A pelleted acid treated sub-bentonite clay containing 1.34% F8203 (dry basis) was treated with a sulfiding gas of the composition above described at 1350-1400 F. for 4 hours, then leached with dilute hydrochloric acid at room temperature, washed and dried. The final catalyst contained 0.15% Fezoa and showed a cracking activity by the CAT-A method of 39.6 volume percent gasoline, 3.3 Weight percent coke and 9.4 weight percent gas of 1.65 gravity.

Although nitrogenous gases of the composition hereinbefore described are readily and economically obtained from flue gas, it will be understood that the invention is not limited to any particular source or manner of obtaining essentially inert gaseous carriers of the composition described.

Obviously many modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim as my invention:

1. In processes for the beneflciation of iron containing clays by methods involving the steps of sulfldation of a clay at elevated temperature followed by acid leaching, the improvement which comprises heating the clay to such elevated temperature by contact with 1101; treating .gas composed of an active sulfiding gas and a predominant quantity offan essentially. inert gaseous carrier composed chiefly of nitrogen,

. said treating gas being free from water in excess of 5% by volume and free fromsubstances V reacting to form waterjiri excess of said amount of water under the treating conditions, "said I reating gas being further free from CQz in fex- "cess of 15% by volume.

, 2. The improvement. define d in claim in which said treating gas contains carbondioxide in an: amount ,less than that giving a volume ratio of COz/I-I zS above 10.]

3. The improvement defined in claim 11in which said ,treatinggas, comprises less than 10% by volume of carbon dioxide.

4. The improvement defined in claim 1 in which said essentially inert gaseous carrier contains small amounts of at least one gas from the group consisting of hydrogen and carbon monoxide, not in excess of 3% hydrogen and 5% carbon monoxide by volume of said treating gas.

5. The improvement as defined in claim 1 in which said essentially inert gaseous carrier is flue gas obtained by the controlled combustion of a gaseous fuel so that the flue gas is substantially free of uncombined oxygen.

6. The improvement defined in claim 1 in which said treating gas comprises 0.5 to 25% by volume of hydrogen sulfide as the active sulflding gas.

7. The improvement defined in claim 1 in which said treating gas contains over by volume of nitrogen.

8. The process according to claim 1 in which said active sulfiding gas is carbon disulfide.

9. The process of preparing improved catalysts from iron-containing clay, which comprises treating said clay at elevated temperature with a mixture of gases comprising an essentially inert gaseous carrier and 0.5 to 25% hydrogen sulfide and thereafter acid leaching the thus sulflded clay, said mixture of gases containing predominantly nitrogen being free from C0: in excess of 15% by volume and being free from water in excess of 5% by volume and being also free from substances reacting to form water in excess of said amount of water under the treating conditions.

10. The process of preparing improved catalysts from clay containing iron compounds, which comprises treating said clay with a diluted sulflding gas at a temperature above 1200 F. for a time suflicient to convert the iron compounds to sulfides, said diluted sulfiding gas comprising as an essentially inert gaseous heat carrier dried flue gas substantially free from uncombined oxygen, and being also free from carbon dioxide in excess of 15% by voume of the total gaseous mixture, and thereafter subjecting the sulflded clay to treatment to remove iron sulfides formed.

11. The process of preparing improved catalysts which comprises subjecting an acidtreated montmorillonite clay containing iron compounds to sulfidation at a temperature of 1350-1450 F. with a sulflding gas selected from the group consisting of carbon disulflde and hydrogen sulfide, diluted with an essentially inert carrier gas comprising predominantly nitrogen, and thereafter acid leaching the'thus sulflded clay; said treating gas being free from water in excess of 5% by volume and free from substances reacting to form water in excess of said amount of water under the treating conditions,

said treatinggasibeing' further 'free' "irom C62 in" excess of 15%1by volume;

12. The process of claim 11 inwh'ich "the su' lfidinggas composition includingthe essentially inert carriergas comprises by volume: 0.5 to25'% hydrogen sulfide, carbon dioxide in anxamount less than 15%, up, to 5% carbon monoxide, the

balance of the composition "being madeup chiefly of nitrogen.

71'3.$The process ofclaim 11 in which said essentieilly inert carrier gas, comprise 0.5 'to 3.0%

hydrogen, 1;0"to 4.5% C0,]11t0 13% CO2, the balance of the composition being essentially nitrogen.

HUBERT A. SHABAKERI;

gee-1:422

. l2 REFERENGESCIIEBI The following references are'of 'ecoi'din flier file of this patent: I

UNITED STATES PATENTS Number Name Date 1,721,441 Parentani Sept; 10, 1929 2,205,409 Houdry June-25,1940 2,388,302 Weyl Nov. 6, 1945 2,456,326 -Rupp et a1. Dec. 14, 1948 2,465,048 Shabaker etai. Apr, 5,1949 2,466,052 Shaba'ker etal. Apr. 5; 1949 Certificate of Correction Patent No. 2,561,422 July 24, 1951 HUBERT A. SHABAKER It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows Column 1, line 32, for as read at; column 2, line 15, for that portion of the equation reading 3Fe S read 21 6 8 column 6, line 41, for is has read it has; columns 7 and 8, Table 1, ninth column thereof, in the heading,

for that portion reading H S/Fe O read Ho /F6 0 column 9, Table 2 column seven thereof, line 3, for 84: read 8.4; column 10, line 59, for Voume read volume;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 23rd day of October, A. D. 1951.

a THOMAS F. MURPHY,

' Assistant Commissioner of Patents. 

1. IN PROCESS FOR THE BENEFICIATION OF IRONCONTAINING CLAYS BY METHODS INVOLVING THE STEPS OF SULFIDATION OF A CLAY AT ELEVATED TEMPERATURE FOLLOWED BY ACID LEACHING, THE IMPROVEMENT WHICH COMPRISES HEATING THE CLAY TO SUCH ELEVATED TEMPERATURE BY CONTACT WITH HOT TREATING GAS COMPOSED OF AN ACTIVE SULFIDING GAS AND A PREDOMINANT QUANTITY OF AN ESSENTIALLY INERT GASEOUS CARRIER COMPOSED CHIEFLY OF NITROGEN, SAID TREATING GAS BEING FREE FROM WATER IN EXCESS OF 5% BY VOLUME AND FREE FROM SUBSTANCES REACTING TO FORM WATER IN EXCESS OF SAID AMOUNT OF WATER UNDR THE TREATING CONDITIONS, SAID TREATING GAS BEING FURTHER FREE FROM CO2 IN EXCESS OF 15% BY VOLUME. 